Hot-gas engine with displacer cap safety venting means



y 1952 F. VAN WEENEN 2,596,058

HOT-GAS ENGINE WITH DISPLACER CAP SAFETY VENTING MEANS Filed April 12,1946 INVENTOR. Frunciscus Lumber'rus Von Weenen Patented 'May 6, 1952HOT-GAS ENGINE WITH DISPLACER 'GAP SAFETY VENTING .MEAN S FranciscusLambertus van Weenen, Eindhoven, Netherlands, assignor, by mesneassignments, to Hartford National BankandTrus't Company, Hartford, Conn,as trustee Application April 12, 1946, Serial No. 661,629

3 Claims.

With hot-gas engines it is known to provide the displacer which isadapted to move in the hot chamber of the engine with a cap of poorheat-conductive material. This cap has primarily the function ofsecuring thermal insulation between the hot and the cold chambers of theengine, said chambers :being separated by the displacer.

In order that the good heat-insulating properties of a displacerprovided with such a cap may be fully utilised it is desirable that theconnection between this cap and the displacer should be gas-tight. Thisis also desirable in view of the fact that if this connection would havea slight leakage of air, useless work would be performed by the enginesin order to pump the medium into and out of the cap. Truly in thepresence of a very small leak in this connection this pumping would notyet lead to appreciable losses, but when the engine has .run for aconsiderable time at a very high pressure level the presence of such asmall leak may cause the pressure in the cap to assume a high value. Onthe pressure level in the engine being then suddenly lowered, the capmay be pushed off the displacer by the much higher gaseous pressureprevailing in it, unless there is a very heavy and hence frequentlyinconvenient attachment between the cap and the displacer. To obviatethis difiiculty, a solder joint between the cap and the displacer hasgenerally been provided in hot gas engines.

The present invention provides the possibility of adopting a materiallysimpler but satisfactory method of attachment between the cap and thebody to which this cap is secured.

The hot-gas piston engine (hot-gas engine, refrigerating machine workingon the reversed hot gas engine principle), in which the pistonlike bodythat moves in the machine space in which or adjacent which caloricenergy is absorbed by the medium active in the machine, has secured toit a cap of poor heat-conductive material. In the arrangement disclosedherein this cap is set tightly on the said body by a screw attachmentand the space between the cap and the piston-like body is in permanentcommunication with a further space in which the pressure at a givenmoment is at the utmost no more than equally high as the pressure whichat that moment prevails in the cycle of operations in the machine, itbeing structurally simple to cause the space between the cap and thepiston-like body to be in communication with the crank chamber of themachine, because if this chamber, as is the standard practice, is shutoff from the surthe Netherlands c'to'ber29, 1945 (C1. Bil-24) active inthe machine or to roundings in which the machine is arranged a pressureprevails in it which is about equal to the mean pressure level in themachine or is lower than this pressure. If thus at a given moment theworking medium should leak unexpectedly, through the connection betweenthe cap and the displacer into the cap, it is possible for this mediumto leak away in turn in an unhampered manner through the said connectionto the crank chamber. This connection may be formed by a recessedportion in the displacer connecting rod or else by a pipe provided inthe machine for this purpose.

Guided by the idea on which the present invention is based its sufiicesto use a simple screw connection, such as a central screw boltconnection, for the attachment of the cap to the associated piston-likebody.

In order that the invention may be clearly understood and readilycarried into effect it will now be described more fully with referenceto the accompanying drawing, in which a hot gas piston machine isdiagrammatically shown.

Referring to the single figure of the drawing, l designates the housingof the machine, 2 the cylinder liner, 3 the crank chamber, t thedisplacer, 5 the cap which is secured to the displacer and is made ofmaterial having poor heat conducting properties, such as vanadium alloysteel, '6 the piston, l the piston connecting rod, 8 the crank, 9 thecrank shaft, H] the displacer connecting rod, ll, l2, l3 and M the rodswhich couple the expeller connecting rod to the piston rod 1 and whichserve to cause the displacer 4 to move with the desiredphase-displacement relatively to the piston I. In addition, l5 and I6designate the two devices which serve respectively to supply caloricenergy to the medium withdraw this energy from this medium and I! theregenerator. From the chamber [8 arranged over the displacer 4, themedium active in the machine flows via the heat exchanger l5, theregenerator l'!, the heat exchanger l6 to the space l9 between the lowerside of the displacer 4 and the upper side of the piston 6 and viceversa. If the hot gas piston machine is constructed to form a, hot gasengine, the medium active in the engine is caused to assume the requiredtemperature by heat from without via the heat exchanger l5 and themedium is cooled via the exchanger It. In this case, a temperatureprevails in the chamber I8, which is then referred to as the hotchamber, which is materially higher than the temperature in the chamberl9, which is then referred to as the cold chamber. If the hot gas pistonmachine is in tended to operate as a refrigerating machine, the heatexchanger I5 is arranged in the surroundings to be cooled and a lowertemperature prevails in the chamber l8, then referred to as cooledchamber, than in the chamber l9 (hotter chamber) the caloric energyabsorbed by the heat exchanger being conducted away by means of the heatexchanger 16 at a higher temperature.

Now, if, as stated herein-before, the cap 5 would be secured to thedisplacer 4 by a soldering joint and this joint would inadvertently havea small leakage of air, the space within the cap, if the medium activein the machine is at a very high pressure, is gradually filled withmedium which also is at a very high pressure. If the pressure in themachine is then suddenly lowered to a very great extent,for example inconnection with the control of the machine, the space within the cap isstill at the originally high pressure and there is the risk that afterthe breakdown of the soldering joint the cap 5 is pushed ofi thedisplacer 4 by this high pressure with the result that the machine getsout of order. Now, in the form of construction of the machine accordingto the invention as shown on the drawing this is avoided by causing thespace in the cap 5, by means of the pipe 20 which extends through thepiston body 6, permanently to communicate with the space inside thecrank chamber 3, which is shut off from the surroundings, so that thepressure prevailing within the cap never exceeds that in the crank case3. takin particular measures to secure the cap 5 to the displacer 4 in aparticularly solid matter, so that in the case shown it suflices tosecure this cap to the displacer body 4 by means of a single centralscrew bolt 2|. It is only natural that by the provision of fitting edgesor the like care will be taken that the connecting edge between the cap5 and the displacer 4 is gas-tight, because there would otherwise be theprobability of leakage of the working medium from the machine space viathe pipe 20 to the crank case.

What I claim is:

1. In a hot gas engine, the combination of a displacer element, capmeans attached to said displacer and forming an enclosed spacetherebetween, a closed crank case, crank means in said crank case, meansoperatively connecting said displacer with said crank means in saidcrank This avoids the need for s 4 7 case, and fluid conducting meansdirectly connecting said enclosed space with said closed crank casewhereby the pressures in said enclosed space and said enclosed crankcase are maintained substantially equal.

2. In a hot gas engine, the combination of a casing, a displacer elementlocated in the casing, 7

cap means attached to said displacer and enclosing a space therebetween,an enclosed crank case, piston means located in said casing between thedisplacer element and the enclosed crank case to define a chamberbetween said displacer element and said piston means, and tube meansconnecting said enclosed space and said enclosed crank case, said tubemeans passing through but not communicating with said chamber and alsopassing through said piston whereby the pressure in said enclosed spaceand said enclosed crank case are maintained substantially equal.

3. In a hot gas engine, the combination of a casing, a displacer elementlocated in the casing and movable for reciprocatory motion therein, capmeans attached to said displacer and enclosing a space therebetween, anenclosed crank case, crank means in said crank case, means operativelyconnecting said displacer with said crank means in said crank case,piston means located in said casing between the displacer element andthe enclosed crank case to define a chamber between said displacerelement and said piston ,means, means operatively connecting said pistonmeans with said crank means, and fluid conducting means directlyconnecting said enclosed space and said enclosed crank case, said fluidconducting means passing through but not communicating with said chamberand also passing through said piston whereby the pressure in saidenclosed space and said enclosed crank case are maintained substantiallyequal.

FRANCISCUS LAMBERTUS VAN l/VEENEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 374,123 Hopkins Nov. 29, 1887942,261 Hubbard Dec. 7, 1909 1,073,065 Anderson et a1 Sept. 9, 19131,730,580 Lundgaard Oct. 8, 1929

